Devices for automatic filling of flexible tubular containers, such as string bags used to contain fruit and vegetables, generally comprise a pair of holding clips which hold the upper opening of the container to be filled, in an open position, while the containers are being filled. Once the container has been filled, it is then sealed, which usually comprises the step of joining the clips holding the container, sealing it at the top to then join two sealing portions, facing one another, on the edge of the upper opening of the container.
In order to ensure the best seal on the container, it is usual to fold the side portions of the container that are between the joined sealing portions, so that the folds produced are interposed, at least partially, between said joined portions. These sides are said to fold or double over like an accordion.
For this purpose, the filling devices comprise folding means each with actuators facing outwards onto the sides of the container to be folded. These actuators move towards the container, pushing both side portions of the container inside the container, while the two sealing portions are joined by bringing together the holding clips. The pushing of these actuators produces a fold in each side of the container in the area close to its upper edge.
In order to ensure the folding of the sides of the container, the actuators must remain partially inside the container, pushing the side portions of the container inside the container, while the two sealing portions are joined. It is also usual for the filling devices to have a holding clip, positioned at a lower level, which closes to fasten the container once it has been filled, to transport the container to a station following that of sealing the fastening, for example, by heat-sealing the joined sealing portions in the filling station.
To date, two single actuators are used that produce a single fold in each side of the container, a fold that is made in the middle of each side, or in other words, centred with respect to the width of the container. This is because the presence of the actuators must not prevent the holding clips from coming together to seal the top of the container.
On many occasions, it is of particular interest to produce more than one fold in the container sides as long as the two sealing portions join to seal the top of the container, but no device is known to exist for multiple folding, while allowing the container to be sealed automatically as this operation does in filling devices of the type described earlier.
It should also be mentioned that the actuators of said devices usually introduce excess pressure on the wires or tapes comprising the mesh of the containers when the actuators push the respective side portions of the containers inwards. This excess pressure may damage or even break the mesh comprising the containers during subsequent handling of the filled containers.